Abstract

We show that a pinhole camera can be designed based on the defocus aberration, and obtain the same result as the one obtained by Petzval by minimizing the image spot radius representing the sum of the geometrical and diffraction contributions to it. It is well known that defocus aberration degrades an image. However, we show that the axial irradiance of a beam focused with a small Fresnel number is higher than the focal-point value. We also show that the irradiance increases when spherical aberration is introduced, contrary to the general expectation that it should decrease. Finally, we consider two-point resolution and show how a defocus aberration changes the relative illumination of the images of two coherent points.

© 2014 Optical Society of America